The recently discovered Human B-Cell Lymphotropic Virus (HBLV), also known as Human Herpes Virus Type 6 (HHV-6) has been implicated in playing a role in various lymphoproliferative diseases including chronic mononucleosis-like syndrome, B-cell lymphomas, and AIDS. In Phase I of this grant, we have developed a non-radioactive DNA probe for HBLV, and have demonstrated its usefulness in detecting HBLV sequences in lymphocytes and tissues. Preliminary examination of tumor tissues from Burkitt's Lymphoma and other B-cell lymphoma patients using this assay has shown that HBLV sequences are present in many of these tumors, and occur in quite high levels in some of them. In Phase II, these studies will be extended to a larger number of samples. The in situ hybridization system will be made available to other researchers and will be further optimized to permit its routine use in the clinical laboratory. A DNA "Sandwich" assay will also be developed for the direct detection of virus in blood samples. This assay will utilize very simple sample handling conditions and will be compatible with existing ELISA formats. Exquisite sensitivity (to less than 10 copies of the viral genome) will be achieved by combining the DNA sandwich assay with the Polymerase Chain Amplification system. The in situ and DNA sandwich hybridization assays will be commercialized and will provide powerful diagnostic tools to researchers and clinicians studying lymphoproliferative disorders.